1. Field of the Invention
The present invention relates to an image processing apparatus, a control method therefor, and a control program.
2. Description of the Related Art
There has been proposed a technique in which copy restriction information and history information are embedded in a printed document, and a copying operation is restricted based on the embedded information, to thereby maintain the security of the printed document (see e.g. Japanese Laid-Open Patent Publication (Kokai) No. 2004-228897).
However, in order to embed copy restriction information and history information in a printed document, the printed document requires an empty area larger than a predetermined size, where no print image is printed, and when a print image occupies a major portion of a sheet area, it is impossible to secure a sufficient empty area.
To solve this problem, it is envisaged to employ a technique in which embedded information is embedded in the back side of a sheet such that the embedded information can be read by reading images on the respective front and back sides of the sheet before copying.
However, the above-mentioned conventional technique suffers the following problems: When embedded information may be embedded on the back side of a sheet, it is impossible to determine whether or not the embedded information is actually present on the back side of the sheet, simply by reading an image on the front side of the sheet. For this reason, it is absolutely required to read both front-side and back-side images for every sheet, so as to maintain security. Therefore, even when a printed document has no embedded information on the back side thereof and has only a front-side image to be read, it is required to perform double-sided image reading, which causes degradation of reading efficiency.